This invention relates to printing blankets and more particularly to printing blankets of the type used in offset lithographic printing.
In lithographic printing, a printing blanket is employed to transfer printing ink from a printing plate to n article such as paper, or the like, being printed and such printing blanket is operated under tension and brought into repeated contact with its associated printing plate and paper.
During ordinary usage of printing blankets, press operators tension such blankets over a substantial tension range which may vary from 25 pounds per inch of blanket width to as high as 100 pounds per inch even though in most applications 50 pounds per inch of width is recommended. However printing blankets proposed heretofore are deficient in that they are not capable of operating over a substantial range of blanket tension; and, when such blankets are operated near the high end of the above range of tensions they tend to become permanently stretched or deformed which causes a reduction in print quality. Another deficiency of printing blankets in common use is due to the utilization of fabric layers therein which are made entirely of materials which tend of wick solvents coming into contact with associated side edges of such blankets. Wicking is a difficult problem to solve because even though sealers are employed to prevent such wicking, the seal initially provided by a particular sealer is often broken during blanket use allowing solvents to penetrate the blanket and reach edges of fabric material in the blanket whereupon such material loses its properties, relaxes, and stretches thereby allowing the blanket to stretch.